A linear image sensor is used for an input device of a picture in an office automation apparatus, such as a facsimile, an intelligent copper and the like. In a conventional image element, picture information generally is obtained from a (CCD type or MOS type) linear solid image sensor by way of exposing a picture through a slit to light and focusing it into image in a smaller scale. The linear solid image element usually has a size of about 30 mm, which is produced by IC technique. However, since the element must adopt an optical system having a long optical path length for introducing reflected light from a manuscript to a receiving part, it is difficult to miniaturize the apparatus. In addition, these types of devices require complicated adjustment of a light path. They may raise problems such as reduction of luminous energy on an edge portion of picture, decline of a resolution and the like.
For improving the above problems, there have been proposed contact type image sensors which have the same size as manuscripts in length and which contactly focus into image by a fiber lens array. In the contact type image sensors, photoelectric conversion parts have to be made large and uniform.
Presently, for producing long size image sensors, amorphous silicon thin film has been used, but, in these silicon image elements, a strange reading process is required because rising current from the silicon thin film is very weak. For rapid reading, the number of required switches increase, which make the device costly.
On the other hand, contact type image elements using CdSe compound semiconductor as a photoelectric film, can provide signal outputs at a high level, which makes it possible to adopt a real-time reading process. In addition, it makes possible a matrix device and the number of switch elements decrease, which are merits of these types image elements. However, though the photoelectric film is usually formed by vacuum evaporation, it is difficult to obtain reproducibility because a chemical composition can vary by producing conditions.